This invention relates to a propeller-type wind turbine used in wind-powered electrical generation.
Because of its mountainous terrain, Japan, unlike Europe and elsewhere, is not blessed with steady, strong winds suited to the generation of electricity by wind power. In nearly all regions of Japan, the average annual wind speed is generally under 10 m/sec, and this is usually far below the rated output of a wind-powered electrical generator.
The amount of electricity generated by a wind turbine is as follows:
xe2x80x83Generated amount Wxe2x88x9dxcfx81(density)xc3x97A(wind receiving surface area)xc3x97V(wind speed).
Therefore, the conventional approach to increasing the amount of electricity generated by a wind turbine has been to increase the diameter of a rotor and develop large-scale machines.
The rated wind speed corresponding to the rated output of such large-scale machines is generally quite high (at least 10 m/sec), and it is rare to find an area where such high wind speeds are consistently in effect under ordinary weather conditions (that is, other than during typhoons and other storms), and at present such machinery operates at an output far below its rated output under normal wind conditions. Thus, when a large-scale machine is installed, the improvement in performance at low speed is not commensurate with the higher installation costs entailed by the larger structures (such as generators) required. Furthermore, a large wind receiving surface area makes it more difficult to cope with storm winds, so there is a higher level of danger as well.
It is therefore an object of the present invention to provide a power-generating propeller-style wind turbine with which power generation performance can be improved even in a low speed range.
One embodiment of the present invention is a power-generating propeller-style wind turbine provided with a plurality of turbine blades distributed equiangularly within a plane perpendicular to a horizontal rotating shaft and around a hub provided on the rotating shaft, characterized in that a blade body of each turbine blade includes therewithin a tip auxiliary blade housed to be capable of extending toward and retracting away from a blade tip, and an auxiliary blade extension-and-retraction unit for protruding the tip auxiliary blade toward the blade tip so as to increase an overall length of the blade.
With this structure, when wind speed is low, the tip auxiliary blade extension-and-retraction unit protrudes the tip auxiliary blades and elongates the overall length of the wind turbine blades, which increases lift of the vanes, raises rotating torque, and increases an amount of power generated. If the wind speed is so high that it exceeds a rated output (such as during a storm), the tip auxiliary blades can be retracted and stowed inside the blade bodies, which reduces drag of the turbine blades so that the structure is not subjected to excess load and damage can be prevented.
Another embodiment of the present invention is directed to a power-generating propeller-style wind turbine provided with a plurality of turbine blades distributed equiangularly within a plane perpendicular to a horizontal rotating shaft and around a hub provided on the rotating shaft, characterized in that a blade body of each turbine blade includes therewithin a tip auxiliary blade housed in the blade body able to extend towards and retract away from a blade tip, and an auxiliary blade extension-and-retraction unit for protruding the tip auxiliary blade toward the blade tip so as to increase an overall length of the blade, a leading edge auxiliary vane having an airfoil-shaped cross section capable of forming, between the vane and the blade body, a path for guiding an airflow to a rear face of the blade body, which is disposed at a leading edge portion of the blade body of each turbine blade so as to be capable of extending and retracting frontward in a rotational direction and a leading edge auxiliary vane extension-and-retraction unit for protruding the leading edge auxiliary vane frontwardly in the rotational direction and guiding the airflow from the formed path thus formed to the rear face of the blade body, thereby generating lift on the leading edge auxiliary vane and increasing a rotating torque of the turbine blade.
With this structure, lift will be generated at the tip auxiliary blades and the leading edge auxiliary vanes and the rotating torque will be further increased even though the incoming airflow is moving more slowly because of the tip auxiliary blades and the leading edge auxiliary vanes, thereby expanding the range of low wind speeds at which power generation is feasible.
Yet another embodiment of the present invention is a power-generating propeller-style wind turbine provided with a plurality of turbine blades distributed equiangularly within a plane perpendicular to a horizontal rotating shaft and around a hub provided on the rotating shaft, characterized in that a blade body of each turbine blade includes therewithin a tip auxiliary blade housed to be capable of extending toward and retracting away from a blade tip, and an auxiliary blade extension-and-retraction unit for protruding the tip auxiliary blade toward the blade tip so as to increase an overall length of the blade; a leading edge auxiliary vane having an airfoil-shaped cross section capable of forming, between the vane and the blade body, a path for guiding an airflow to a rear face of the blade body which is disposed at a leading edge portion of the blade body of each turbine blade so as to be capable of extending frontwardly in a rotational direction; a leading edge auxiliary vane extension-and-retraction unit is provided for protruding the leading edge auxiliary vanes frontward in the rotation direction and guiding the airflow from the path thus formed to the rear face of the blade body, so as to generate lift on the leading edge auxiliary vane and to increase a rotating torque of the turbine blade; and wherein the blade body of each turbine blade includes a rear auxiliary vane provided at a trailing edge portion and being capable of extending and retracting rearwardly in the rotational direction, and a rear auxiliary vane extension-and-retraction unit for protruding the rear auxiliary vane to extend rearwardly so as to increase a vane arc length.
With this structure, because of the increase in lift produced by the leading edge auxiliary vanes, the increase in lift produced by the tip auxiliary blades, and the increase in lift produced by increasing the vane arc length and/or vane camber with the leading edge auxiliary vanes and the trailing edge auxiliary vanes, more lift is generated at the turbine blades, the rotating torque is heightened, and the amount of electricity can be increased even with a low speed airflow.
The present invention also includes a structure as set forth above and including a pitch changing guide member for changing a pitch of the tip auxiliary blade is provided to an extension-and-retraction unit that guides the tip auxiliary blade to extend and retract.
With this structure, the pitch changing guide member allows the pitch of the vane bodies to continuous with that of the tip auxiliary blades, forming a vane of a better performance.
Still yet another embodiment of the present invention is a power-generating propeller-style wind turbine provided with a plurality of turbine blades distributed equiangularly within a plane perpendicular to a horizontal rotating shaft and around a hub provided on the rotating shaft, characterized in that a leading edge auxiliary vane having an airfoil-shaped cross section capable of forming, between the vane and the blade body, a path for guiding the airflow to a rear face of the blade body which is disposed at a leading edge portion of the blade body of each turbine blade so as to be capable of extending and retracting frontwardly in a rotational direction; and a leading edge auxiliary vane extension-and-retraction unit is provided for protruding the leading edge auxiliary vanes frontwardly in the rotational direction and guiding the airflow to the rear face of the blade body, thereby generating lift on the leading edge auxiliary vane and increasing a rotating torque of the turbine blade.
With this structure, lift will be generated at the leading edge auxiliary vanes and the rotating torque will be increased even though the incoming airflow is moving slowly, thereby expanding the range of low wind speeds at which power generation is feasible.
The present invention also includes a blade body of each turbine blade includes a rear auxiliary vane provided at the trailing edge portion and being capable of extending and retracting rearwardly in the rotational direction, and a rear auxiliary vane extension-and-retraction unit for protruding the rearwardly so as to increase a vane arc length.
With this structure, because of the increase in lift produced by the leading edge auxiliary vanes and the increase in lift produced by increasing the vane arc length and/or vane camber with the rear auxiliary vanes, more lift is generated at the turbine blades, the rotating torque is heightened, and the amount of electricity can be increased even with a low speed airflow.
Yet another embodiment of the present invention is a power-generating propeller-style wind turbine provided with a plurality of turbine blades distributed equiangularly within a plane perpendicular to a horizontal rotating shaft and around a hub provided on the rotating shaft, characterized in that the blade body of each turbine blade includes a rear auxiliary vane provided at a trailing edge portion and being capable of extending rearwardly in a rotational direction, and a rear auxiliary vane extension-and-retraction unit for protruding the rear auxiliary vane rearwardly so as to increase a vane arc length.
With this structure, the rear auxiliary vanes increase the vane arc length and/or the vane camber, and as a result, increase the lift generated at the turbine blades thereby to increase the rotating torque, so that more electricity can be generated even with a low speed airflow.